Preparation of a high-hiding and deeply colored pigmentary form of perylene-3,4,9,10-tetracarboxylic acid bis-(4'-ethoxyphenyl)-imide

Abstract

A process for the preparation of a high-hiding, deeply colored pigmentary form of perylene-3,4,9,10-tetracarboxylic acid bis-(4'-ethoxyphenyl)-imide by heating the finely divided crude pigment, which is in the form of agglomerates, formed from primary particles of length 0.15 μm or less, in cyclohexanone or a mixture of cyclohexanone and water at from 30° to 200° C., and isolating the pigment.

I claim: 
     
       1. A process for the preparation of a high-hiding, deeply colored pigmentary form of perylene-3,4,9,10-tetracarboxylic acid bis-(4'-ethoxyphenyl)-imide by heating the finely divided crude pigment, in the form of agglomerates formed from primary particles of length 0.15 μm or less, in an organic liquid or a mixture of an organic liquid and water at from 30° to 200° C., and isolating the pigment, in which process cyclohexanone is used as the organic liquid. 
     
     
       2. A process as claimed in claim 1, wherein a mixture of cyclohexanone and water in a weight ratio of from 10:1 to 1:10 is used. 
     
     
       3. A process as claimed in claim 1, wherein a mixture of cyclohexanone and water in a weight ratio of from 1:6 to 3:1 is used. 
     
     
       4. A process as claimed in claim 1 or 2, wherein from 3 to 20 parts by weight of liquid are used per part by weight of crude pigment. 
     
     
       5. A process as claimed in claim 1 or 2, wherein the mixture is heated at from 30° C. to the boiling point of the liquid phase under atmospheric pressure. 
     
     
       6. A process as claimed in claim 1, wherein after the heating the cyclohexanone is removed by steam distillation and the pigment is isolated. 
     
     
       7. Perylene-3,4,9,10-tetracarboxylic acid bis-(4'-ethoxyphenyl)imide in a pigmentary form obtained according to the process of claim 1.